1. Field of the Invention
The present invention relates to a method and system for forming a composite material by resin transfer molding.
2. Description of the Related Art
Composite materials are typically formed by impregnating a fibrous sheet with a thermosetting organic resin. To create the composite material, the fibrous sheet is typically placed on a tool which has a pattern corresponding to the desired shape of the composite. The sheet is then encapsulated by a cover plate that is fastened to the tool.
A vacuum is pulled within the inner cavity of the tooling to remove gaseous and liquid impurities from the cavity. A resin is then pumped into the inner cavity. The inner cavity is subsequently heated to cure and form the composite material.
The resin is typically pumped into the inner tool cavity at pressures ranging from 30-250 psi. The tooling must be strong enough to withstand such high pressures. Consequently, tooling for forming composite materials is typically constructed from thick metal plates. Thick metal plates are heavy and difficult to carry and maneuver. Additionally, the large mass of the tooling has a relatively high thermal capacitance, thereby requiring extended time periods to heat and cool both the tooling and the part. It would be desirable to provide a resin transfer molding process and system that did not require large tooling plates.
Because of the woven nature of the fibrous pre-formed structure, it is sometimes difficult to fit the sheet between the tool and the cover plate. The fibrous sheet may create a gap between the tool and the cover, which decreases the pressure within the inner tool cavity and causes a variation of resin content in the final composite. The mismatch between the sheet and the tooling may also damage the fibers within the preform. Present resin transfer molding techniques also tend to produce a composite material which has a non-uniform distribution of resin throughout the composite. It would be desirable to provide a resin transfer molding process and system that would provide a more even distribution of resin throughout the composite and which would allow the fibrous sheet to easily fit within the tooling.